11
December 2003
Fisheries: Stock taken
This is the time of the year when the European Commission makes its proposals for fishing quotas in EU waters for the following year. The expert advice (from the International Council for the Exploration of the Sea, www.ices.dk), is that if stocks are to recover there should be a total ban on fishing for cod in the North Sea, Irish Sea and off west Scotland. How have cod stocks collapsed to such a parlous state? Overfishing is often blamed. But a study of the key biological mechanisms by which changes in temperature affect cod larval survival puts a new perspective on things. Rising temperatures since the mid-1980s have led to decreasing survival of cod larvae in the plankton ecosystem. Prey have become too small or are not present at the right time of year, and the abundance of euphausiids, a rich source of energy and vitamin A, is at an all-time low. The net result is that North Sea cod have become more vulnerable to year-to-year environmental variation. Overfishing is a major factor, but the decreasing survival rate of young cod in warming waters has also contributed to the collapse in cod stocks.
Plankton effect on cod recruitment in the North
Sea
GRÉGORY BEAUGRAND, KEITH M. BRANDER, J. ALISTAIR LINDLEY,
SAMI SOUISSI & PHILIP C. REID
Nature 426, 661–664 (2003); doi:10.1038/nature02164
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